Technical Abstract: Sensor-based technologies for in-season application of nitrogen (N) to winter wheat (Triticum aestivum L.) have been developed and are in use in the southern Great Plains. There is little information about the suitability of this technology for spring wheat production in the northern Great Plains. Field experiments were established in Brookings and Gettysburg, SD to evaluate the GreenSeeker Hand Held optical sensor (NTech Industries, Ukiah, CA) for measuring in-season N status on spring wheat. Five N rates were applied pre-plant as ammonium nitrate. Sensor readings and plant biomass samples were collected at Feekes 6 and Feekes 10 growth stages. The sensor measures reflectance in the red and near infrared (NIR) regions of the electromagnetic spectrum and calculates the normalized difference vegetation index (NDVI). The ability of the sensor readings to measure biomass, plant N uptake, and predict grain yield and protein for each sampling date was determined. In general, in-season plant biomass, plant N concentration, and grain yield increased with increasing N rate. Sensor readings (NDVI) collected at Feekes 6 and Feekes 10 showed a significant relationship with plant biomass, N uptake and grain yield, with readings collected at the later growth stage having higher correlations compared to the early sampling date. Initial results suggest that existing sensor-based variable nitrogen technology developed for winter wheat could be utilized in the northern Great Plains for estimating in-season N need for spring wheat, but additional testing is necessary.